1. Field of the Invention
The invention relates generally to an electromechanical fastener driving tool, and, in particular, to a fastener driving tool which uses a cone clutch to couple a flywheel to a fastener driving device.
2. Description of the Prior Art
Prior art workers have devised many types of mechanically operated fastener driving tools utilizing driving means actuated pneumatically, electromechanically or by internal combustion. To date, pneumatically actuated fastener driving tools are the ones most frequently encountered. While pneumatically actuated tools work well and have become quite sophisticated, they nevertheless require the presence of a compressor or the like.
There are many job sites where a source of compressed air is not normally present. This is particularly true of smaller job sites and the like. On the other hand, electricity is almost always present on such sites. As a consequence, particularly in recent years, prior art workers have directed considerable attention to electromechanical tools.
Some prior art electromechanical tools depend upon a heavy duty solenoid to do the fastener driving. In general, however, such tools are not adequate where large driving forces are required or desired. As a consequence, prior art workers have also expended considerable thought and effort in the development of electromechanical fastener driving tools employing one or more flywheels. Examples of such tools are taught in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,204,622; and 4,298,072. Yet another example is taught in British Pat. No. 2,000,716.
It will be evident from these patents that prior art workers have devoted a great deal of time to the development of flywheel fastener driving tools. Nevertheless, such tools do present their own unique problems. For example, in tools utilizing two flywheels, it has been the practice to provide a separate electric motor for each flywheel. This adds considerably to the weight and bulk of the tool and is difficult to synchronize. Another approach is to mount one of the flywheels on the electric motor shaft and then drive the second flywheel through a series of belts or chains and pulleys. Such drives are complex, difficult to adjust, and are subject to wear.
Another problem area involved means to cause one of the flywheels to move toward and away from the other. Preferably, for example, one of the flywheels is capable of shifting toward the other and into an operative position wherein its periphery is spaced from that of the stationary flywheel by a distance less than the nominal thickness of the thick part of the driver. The same flywheel is shiftable in the opposite direction to an inoperative position wherein its periphery is spaced from that of the fixed flywheel by a distance greater than the greatest nominal thickness of the driver. Heretofore, systems to bring about this shifting of one of the flywheels with respect to the other have been cumbersome, complex and not altogether satisfactory.
Yet another area of concern has involved means for returning the driver at the end of the drive stroke to its normal, retracted position. For these purposes, prior art workers have developed complex systems of springs, pulleys and elastomeric cords. Such systems, however, have proven to be subject to wear, stretching and deterioration due to lubricants and foreign materials within the tool housing. Other systems have employed a powered return roller and an idler roller which shifted a free floating driver to its normal position after the drive stroke. These systems were also found to be less than satisfactory.
Consequently, heretofore there has not been available in the industry a reliable, lightweight and relatively simple electromechanical fastener driving tool which can efficiently drive fasteners of various sizes, particularly those sizes needed in heavy duty framing applications.
However, a novel solution to these problems has been found with the use of a frictional clutch mechanism. These mechanisms are common in other types of mechanical devices. U.S. Pat. Nos. 2,291,151; 4,030,581; 4,416,3590; 4,526,052; and 4,545,469 all teach the use of clutch mechanisms to transfer energy from one mechanism to another. This energy transfer may be accomplished using several different methods. By employing this concept within a fastener driving tool, it is possible to overcome the aforementioned problems which have prevented the prior art electromechanical fastener driving tools from being accepted commercially.